Electrosurgical apparatus for delivering rf and/or microwave energy into biological tissue

ABSTRACT

An electrosurgical instrument for applying to biological tissue RF electromagnetic energy and/or microwave frequency EM energy, wherein the instrument tip has a protective hull with a smoothly contoured convex undersurface facing away from a planar body, and wherein the planar body has a tapering distal edge, and wherein an underside of the planar body extends beyond the protective hull at the tapering distal edge. Also disclosed herein is an interface joint for integrating into a single cable assembly all of (i) a fluid feed, (ii) a needle movement mechanism, and (iii) an energy feed (e.g. a coaxial cable), and a torque transfer device for permitting controlled rotation of the cable assembly within the instrument channel of an endoscope. The interface joint and torque transfer device may be integrated as a single component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.15/109,077, filed Jun. 29, 2016, which is a National Stage entry ofInternational Application No. PCT/GB2014/053857, filed Dec. 31, 2014,which claims priority to British Patent Application No. 1323171.7, filedDec. 31, 2013. The disclosures of the priority applications are herebyincorporated in their entirety by reference.

TECHNICAL FIELD

The invention relates to an electrosurgical apparatus and device fordelivering radiofrequency and/or microwave frequency energy intobiological tissue. In particular, the invention relates to anelectrosurgical instrument capable of delivering radiofrequency (RF)energy for cutting tissue and/or microwave frequency energy forhaemostasis (i.e. promoting blood coagulation). The invention may beparticularly suitable in gastrointestinal (GI) procedures associatedwith the lower and upper GI tract, e.g. to remove polyps on the bowel,i.e. for endoscopic mucosal resection, or endoscopic submucosaldissection. The invention may also lend itself to other procedure, e.g.in general surgery or laparoscopic surgery. The invention may find usein ear, nose and throat procedures and liver resection. The device mayalso be used to address procedures associated with the pancreas, e.g. toresect or remove tumours or abnormalities in close proximity to theportal vein or the pancreatic duct.

BACKGROUND TO THE INVENTION

Surgical resection is a means of removing sections of organs from withinthe human or animal body. Such organs may be highly vascular. Whentissue is cut (divided or transected) small blood vessels calledarterioles are damaged or ruptured. Initial bleeding is followed by acoagulation cascade where the blood is turned into a clot in an attemptto plug the bleeding point. During an operation, it is desirable for apatient to lose as little blood as possible, so various devices havebeen developed in an attempt to provide blood free cutting. Forendoscopic procedures, bleeds are also undesirable, and need to be dealtwith in an expedient manner, since the blood flow may obscure theoperator's vision, which may prolong surgery and potentially lead to theprocedure needing to be terminated and another method used instead, e.g.open surgery.

Electrosurgical generators are prevalent in hospital operating theatres,often for use in open and laparoscopic procedures, and increasingly foruse in endoscopy suites. In endoscopic procedures the electrosurgicalaccessory is typically inserted through a lumen inside an endoscope.Considered against the equivalent access channel for laparoscopicsurgery, such a lumen is comparatively narrow in bore and greater inlength.

Instead of a sharp blade, it is known to use radiofrequency (RF) energyto cut biological tissue. The method of cutting using RF energy operatesusing the principle that as an electric current passes through a tissuematrix (aided by the ionic contents of the cells and the intercellularelectrolytes), the impedance to the flow of electrons across the tissuegenerates heat. In practice, an instrument is arranged to apply an RFvoltage across the tissue matrix that is sufficient to generate heatwithin the cells to vaporise the water content of the tissue. However,as a result of this increasing desiccation, particularly adjacent to theRF emitting region of the instrument (which has the highest currentdensity of the current path through tissue), direct physical contactbetween the tissue and instrument can be lost. The applied voltage thenmanifests itself as a voltage drop across this small void, which causesionisation in the void that leads to a plasma. Plasma has a very highvolume resistivity compared with tissue. The energy supplied to theinstrument maintains the plasma, i.e. completes the electrical circuitbetween the instrument and the tissue. Volatile material entering theplasma can be vaporised and the perception is therefore of a tissuedissecting plasma.

GB 2 472 972 describes an electrosurgical instrument in the form of aspatula comprising a planar transmission line formed from a sheet of afirst dielectric material having first and second conductive layers onopposite surfaces thereof, the planar transmission line being connectedto a coaxial cable that is arranged to deliver either microwave or RFenergy to the planar transmission line, the coaxial cable comprising aninner conductor, an outer conductor coaxial with the inner conductor,and a second dielectric material separating the outer and innerconductors, the inner and outer conductors extending beyond the seconddielectric at a connection interface to overlap opposite surfaces of thetransmission line and electrically contact the first conductive layerand second conductive layer respectively. The first conductive layer isspaced from the end of the transmission line that abuts the coaxialcable to electrically isolate the outer conductor from the firstconductive layer and also the distance of the gap is involved withmatching the impedance of the energy delivered from the microwave sourcewith the impedance of the biological tissue, and the width of the firstand second conductive layers is also selected to help create animpedance match between the transmission line and the coaxial cable.

The spatula configuration set forth in GB 2 472 972 provides desirableinsertion loss between the co-axial feed line and the end radiatingsection, whilst also providing desirable return loss properties for theedges of the spatula when in contact with air and biological tissuerespectively. In more detail, the insertion loss along the structure maybe less than 0.2 dB at the frequency of interest, and the return lossless than (more negative than) −1 dB, preferably less than −10 dB. Theseproperties may also indicate a well matched junction between the coaxialcable and the transmission line spatula structure, whereby microwavepower is launched efficiently into the spatula. Similarly, when theedges of the spatula are exposed to air or biological tissue that is notof interest, the return loss may be substantially zero (i.e. very littlepower radiated into free space or undesirable tissue), whereas when incontact with desirable biological tissue the return loss may be lessthan (more negative than) −3 dB, preferably less than −10 dB (i.e. themajority of power in the spatula is transferred to the tissue).

The instrument discussed in GB 2 472 972 is intended to radiatemicrowave energy from the edges of the planar transmission line to causelocalised tissue ablation or coagulation.

GB 2 472 972 also discloses that the spatula discussed above may have anRF cutting portion integrated therewith. The RF cutting portion may beformed by using the first and second conductive layers mentioned aboveas active and return electrodes for RF energy. This arrangement may takeadvantage of the fact that the active and return electrodes are in closeproximity to one another, thus setting up a preferential return path toenable local tissue cutting action to take place without the need for aremote return pad or a highly conductive liquid, i.e. saline, existingbetween the two electrodes.

In this example, the RF cutting portion may comprise a RF voltage sourcecoupled to the planar transmission line, a frequency diplexer/duplexerunit (or signal adder) comprising a low pass filter to prevent the highfrequency microwave energy from going back into the lower frequency RFenergy source and a high pass filter to prevent the lower frequency RFenergy from going back into the higher frequency microwave energysource. In one example, the frequency diplexer/duplexer may be used toenable the microwave and RF energy sources to be combined at thegenerator and delivered along a single channel, e.g. co-axial cable,waveguide assembly or twisted pair, to the spatula structure. The RFcutting energy may be delivered alone into the tissue or it may be mixedor added with the microwave energy and delivered simultaneously to setup a blended mode of operation.

SUMMARY OF THE INVENTION

The present invention develops further the spatula concept discussed inGB 2 472 972 and the manner with which it interfaces with a generatorthat provides RF and/or microwave energy for treatment.

In a first aspect, the invention provides an further optimisedconfiguration for the distal end of an electrosurgical tool forcontrolled resection of biological tissue.

In a second aspect, the invention provides an interface joint forintegrating into a single cable assembly all of (i) a fluid feed, (ii) aneedle movement mechanism, and (iii) an energy feed (e.g. a cablesupplying RF and/or microwave energy). The cable assembly may be sizedto fit through the instrument channel of a conventional endoscope.

In a third aspect, the invention provides a torque transfer device forpermitting controlled rotation of the cable assembly within theinstrument channel of the endoscope. The interface joint and torquetransfer device may be integrated as a single component.

According to the first aspect of the invention, there is provided anelectrosurgical instrument for applying to biological tissueradiofrequency (RF) electromagnetic (EM) energy and/or microwavefrequency EM energy, the instrument comprising: an instrument tipcomprising a planar body made of a first dielectric material separatinga first conductive element on a first surface thereof from a secondconductive element on a second surface thereof, the second surfacefacing in the opposite direction to the first surface; a coaxial feedcable comprising an inner conductor, an outer conductor coaxial with theinner conductor and a second dielectric material separating the innerand outer conductors, the coaxial feed cable being for conveying an RFsignal and/or a microwave signal; and a protective hull comprising athird piece of dielectric material mounted to cover the underside of theplanar body, wherein the inner conductor is electrically connected tothe first conductive element and the outer conductor is electricallyconnected to the second conductive element to enable the instrument tipto receive the RF signal and/or the microwave signal, wherein theprotective hull has a smoothly contoured convex undersurface facing awayfrom the planar body, wherein the planar body has a tapering distaledge, and wherein the underside of the planar body extends beyond theprotective hull at the tapering distal edge. This combination offeatures represents an optimal configuration that balances the accuracyof treatment at the distal tip (which is enhanced due to the extensionof the planar body over the protective hull) with the ease of safemanipulation of the instrument (due to the protective hull itself).

The portion of the underside of the planar body that extends beyond theprotective hull at the tapering distal edge may be termed the extensionzone. The extension zone may be uniform around the perimeter of thetapering distal edge. Alternatively, the extension zone itself may taperin width towards the distal tip of the planar body. The tapering may bebetween a minimum value at the distal tip and a maximum value at theproximal end of the tapering distal edge. There may be zero extension atthe distal tip, i.e. the protective hull may be contiguous (i.e. flush)with the planar body at that point. The extension zone may be sized toprovide a beneficial impact on the energy fields emitted by the device,but without adversely impacting the function of the protective hull.

The magnitude of the extension zone may be related to, e.g. inproportion to, the geometry of the distal tip. The planar body may haveany dimensions suitable for use in a particular procedure. For example,for endoscopic procedures, the instrument may have an overall outerdiameter of 2.3 mm or less, preferably 1.2 mm or less. The width of theplanar body may thus be 2 mm of less. However, other procedures may beless restrictive, whereby the width of the planar body may be up to 9mm. The width of the extension zone, i.e. the distance by with thetapering distal edge extends beyond the protective hull in a directionnormal to the edge of the protective hull may be 0.2w or less,preferably 0.1w or less, where w is the maximum width of the planar body(i.e. the maximum dimension of the planar body in the direction of thediameter of the lumen or catheter through which it is inserted in use.Thus, for a planar body having a width of 2 mm, the extension zone mayhave a maximum width of 0.2 mm.

In use, the first and second conductive elements may be arranged toprovide a local return path for RF energy, i.e. a low impedance routefor RF energy to be transported between the first and second conductiveelements. The first and second conductive elements may be layers ofmetallisation formed on opposite surfaces of the first dielectricmaterial. The first and second conductive elements may be arranged toset up a local electric field at a contact region in which theinstrument tip makes contact with the biological tissue. The localelectric field can be extremely high, which may cause a microplasma(i.e. a hot thermal plasma) to be formed at the distal side portion ofthe planar body, e.g. where contact is made with the biological tissue.The microplasma may be desirable in terms of achieving efficientcutting.

Meanwhile, for a microwave signal, the instrument tip may be modelled asa parallel plate transmission line with the planar body representingdielectric material separating two conductive plates. The radiationpattern of the microwave frequency EM energy in this case depends on theoverall shape of the planar body and the microwave feed structure. Inthis particular instance, the gap at the proximal end between theco-axial feed line (centre conductor) and the upper conductive layerplays an important role in ensuring that the microwave energy from thesource is matched in terms of impedance with the load impedancepresented by the tissue. The overall length of the planar transmissionline arrangement is also important in terms of matching the impedance(or the energy delivery) of (or from) the coaxial transmission line with(or into) the biological tissue, i.e. the structure may form a quarterwave impedance transformer or a half wavelength resonator. Using knownsimulation tools, this may be modelled to control from which edges themicrowave frequency EM energy is radiated. For example, the instrumenttip may be configured to inhibit radiation of the microwave EM radiationfrom a distal edge of the planar body.

The tapering distal edge may have any suitable profile, e.g. obtained bycomputer modelling the device in particular use configurations. Thetapering distal edge may be curved or straight or a combination of thetwo. For example, the tapering distal edge may comprise a straight taperterminated in a curved distal tip, e.g. a single radius curved distaltip. The tapering distal edge may extends around a distal third ofplanar body. In one embodiment, the curved distal edge may have acurvature formed from a plurality of contiguous radiused sections, eachradiused section having a radius of curvature less than its proximalneighbour. There may be three of more section of different radii. Theplurality of contiguous radiused sections may be arranged to give thecurved distal edge a quasi parabolic shape.

As mentioned above, the width of the planar body may be dictated by theintended use for the instrument. In endoscopic procedures, the width maybe 2 mm or less, whereas for other less restrictive procedures the widthmay be up to 9 mm, e.g. any of 8 mm or less, 7 mm or less, 6 mm or less,5 mm or less, 4 mm or less or 3 mm or less.

The length of the planar body (including the tapering distal end) may berelated to, e.g. in proportion with, its width in order to deliver theRF and/or microwave frequency energy most efficiently. The length of theplanar body may thus be about 5w, e.g. between 5w and 6w, preferably5.3w where w is the maximum width of the planar body.

In one embodiment, the planar body has a maximum width of 2 mm and amaximum length of 10.6 mm. In this embodiment, the tapering distal edgemay comprise a plurality of contiguous radiused sections consisting of afirst radiused section having a length of 1.6 mm and a radius ofcurvature of 12.4 mm, a second radiused section having a length of 1.0mm and a radius of curvature of 10.2 mm, a third radiused section havinga length of 0.7 mm and a radius of curvature of 3.2 mm, a fourthradiused section having a length of 0.2 mm and a radius of curvature of0.85 mm, and a fifth radiused section having a length of 0.1 mm and aradius of curvature of 0.35 mm.

The first and second conductive elements may each comprise a layer ofmetallisation, the layers of metallisation being formed on oppositesurfaces of the first dielectric material. The layers of metallisationmay be set back (e.g. by 0.2 mm) from the side edges of the firstdielectric material in a proximal region of the planar body, to reducethe field strength at this region. The proximal region may comprise theregion of the planar body proximal to the curved distal end. This mayhelp concentrate the energy delivery at the distal end. The innerconductor and outer conductor may contact the first and secondconductive elements in a coaxial manner, i.e. the first and secondconductive elements may be shaped to be symmetric about an axis runningalong the planar body from the coaxial feed cable.

The undersurface of the protective hull may smoothly taper at itsperimeter to meet the underside of the planar body. The thickness of theprotective hull may also decrease towards the distal end of theinstrument tip. Thus, the outer portion of the protective hull may havea convex profile. The undersurface may have a longitudinally extendingrecessed channel formed therein. The tapering edge profile and recessedchannel may cause the undersurface of the protective hull to comprise apair of ridges. The tapered conformal flowing form of the hull mayreduce the risk of the instrument digging into collateral tissue aidingits ability to glide. For example, this shape may reduce the risk of theinstrument digging into the bowel wall and causing a bowel perforationor may protect the portal vein or pancreatic duct from being damaged.The particular dimensions of the hull (e.g. length, width, thickness,etc.) may be adapted to suit the intended use and intended area of thebody to be operated on.

The protective hull may be formed from a biocompatible non-conductivematerial, such as polyether ether ketone (PEEK), ceramic (e.g. alumina,zirconia or zirconia toughened alumina (ZTA)) or biocompatible plasticthat does not stick to the wall of the bowel (or other biologicaltissue) or the like. Alternatively, the hull may also be formed from ametallic material, e.g. titanium, steel, or may be a multi-layerstructure. It may be attached (e.g. bonded) to whichever one of thefirst or second conductive elements is on the underside of the firstdielectric material. However, in one embodiment, the protective hull maybe formed of the same material as the first dielectric material. Theprotective hull and first dielectric material may be formed in one pieceas a unitary body. In this arrangement one or more planar slots may beformed (e.g. cut) in the unitary body to allow a conductive material tobe inserted to form the first and/or second conductive material. Theconductive material may be inserted by coating one or more internalsurfaces of the slot. Alternatively or additionally, the protective hullmay be selectively metallised to form part of the first or secondconductive elements.

The instrument may include a fluid feed conduit for delivering fluid(e.g. saline) to the instrument tip. The fluid feed conduit may comprisea passageway through the protective hull for delivering fluid to thetreatment site. The passageway may include an outlet located in therecessed channel of the protective hull. The coaxial feed cable may formpart of a multi-lumen conduit assembly for delivering RF and/ormicrowave frequency energy and fluid (liquid or gas) to the instrument.The fluid (protective hull) may be conveyed through a correspondingpassageway formed within the multi-lumen conduit assembly. The fluidfeed conduit may also be used to deliver other material to the treatmentsite, e.g. a gas or a solid (e.g. powder). In one embodiment, injectionof fluid (saline or the like) is used to plump up the biological tissueat the treatment site. This may be particularly useful where theinstrument is used to treat the wall of the bowel or the wall of theesophagus or for protecting the portal vein or the pancreatic duct whena tumour or other abnormality located in close proximity, in order toprotect these structures and create a cushion of fluid. Plumping up thetissue in this manner may help to reduce the risk of bowel perforation,damage to the wall of the esophagus or leakage of from the pancreaticduct or damage to the portal vein, etc. This aspect of the invention maymake it capable of treating other conditions where the abnormality(tumour, growth, lump, etc.) is close to a sensitive biologicalstructure.

It is advantageous to be able to use the same instrument to deliverfluid as delivers RF and/or microwave energy since deflation (e.g. dueto fluid seepage or loss of insufflation air) may occur if a separateinstrument is introduced into the region or during treatment. Theability to introduce fluid using the same treatment structure enablesthe level to be topped up as soon as deflation occurs. Moreover, the useof a single instrument to perform desiccation or dissection as well asto introduce fluid also reduces the time taken to perform the overallprocedure, reduces the risk of causing harm to the patient and alsoreduces the risk of infection. More generally, injection of fluid may beused to flush the treatment region, e.g. to remove waste products orremoved tissue to provide better visibility when treating. As mentionedabove, this may be particularly useful in endoscopic procedures.

The undersurface of the protective hull may have a longitudinallyextending recessed channel formed therein, and the fluid deliverymechanism may include an insulating needle guide tube mounted within andextends proximally from the recess channel, and a retractable needle(e.g. hypodermic needle) slidably mounted in the needle guide tube. Theneedle may have an outer diameter less than 0.6 mm, e.g. 0.4 mm. Theneedle may be movable in the longitudinal direction between a deployedposition in which it protrudes beyond the distal end of the instrumenttip and a retracted position in which it is set back from the distaledge of the instrument tip, e.g. below the planar body or locatesproximal to the planar body.

Alternatively, the fluid feed conduit may comprise a tubular (e.g.conical) protrusion integrally formed in the protective hull, e.g. on anundersurface thereof. The tip of the protrusion may have an outlet for afluid passage, and thus may act as a fixed needle-like tip for fluidinjection into the tissue. The tip of the cone may project slightlybeyond the distal tip of the planer body.

According to the second aspect of the invention, there is provided aninterface joint for interconnecting an electrosurgical generator and anelectrosurgical instrument (which may be an instrument according to thefirst aspect of the invention), the interface joint comprising: ahousing made of electrically insulating material, the housing having: afirst inlet for receiving radiofrequency (RF) electromagnetic (EM)energy and/or microwave frequency EM energy from the electrosurgicalgenerator, a second inlet for receiving fluid, and an outlet; a singlecable assembly for connecting the outlet to the electrosurgicalinstrument, the signal cable assembly comprising a flexible sleeve thatdefines a fluid flow path that is in fluid communication with the secondinlet, and which conveys a coaxial cable that is connected to the firstinlet.

The electrosurgical generator may be any device capable of delivery RFEM energy or microwave frequency EM energy for treatment of biologicaltissue. For example, the generator described in WO 2012/076844 may beused.

The electrosurgical instrument may be any device which in use isarranged to use RF EM energy or microwave frequency EM energy for thetreatment of biological tissue. The electrosurgical instrument may usethe RF EM energy and/or microwave frequency EM energy for any or all ofresection, coagulation and ablation. For example, the instrument may bea resection device as disclosed herein, but alternatively may be any ofa pair of microwave forceps, a snare that radiates microwave energyand/or couples RF energy, and an argon beam coagulator.

The housing may provide a double isolation barrier for the operator,i.e. the housing may comprise an outer casing (first level of isolation)that encapsulates a branched passageway (second level of isolation)within which the various inputs are integrated into the single cableassembly. The branched passageway may provide a watertight volume whichdefines a fluid flow path between the second inlet and the outlet, andwhich has a first port adjacent to the first inlet for admitting thecoaxial cable.

In use, the interface joint may be the location at which fluid fortreatment at the instrument is introduced. The operator of the interfacejoint may control the introduction of fluid, e.g. via a syringe or otherfluid introducing mechanism attached to the second inlet. The interfacejoint may also include a fluid delivery deployment mechanism that actsto instruct or control fluid delivery at the electrosurgical instrument.For example, the interface joint may include a slidable trigger on thehousing, the slidable trigger being attached to a push rod that extendsout of the housing through the outlet. The push rod may extend throughthe flexible shaft to the electrosurgical instrument, where it cancontrol the fluid delivery structure. For example, the electrosurgicalinstrument may include a retractable needle that is switchable into andout of fluid communication with the fluid flow path in the flexibleshaft by sliding the push rod back and forth.

In this arrangement, the branched passageway may include a second portadjacent the slidable trigger for admitting the push rod.

Both the first port and the second port may comprise a sealing bungwhich defines a watertight passage for the coaxial cable and the pushrod respectively. The sealing bung may be formed from a resilientlydeformable material, e.g. silicone rubber, whereby the coaxial cable andpush rod are encapsulated in the material as they pass through it.Sealing the first and second ports in this way means that the only routefor fluid out of the interface joint is through the outlet along thefluid flow path in the flexible sleeve.

The branched passageway may have any suitable configuration. In oneembodiment, it is formed from a pair of Y-shaped conduits, which areconnected to each over to define a first length in line with the outlet,a second length extending from a side of the first length at an obliqueangle to the first length, and a third length extending from a side ofthe second length. The first length may have the push rod extendingthrough it and may terminate at is proximal end in a sealing bung. Thesecond length may have the coaxial cable running through it and mayterminate at its proximal end in a sealing bung. The third length mayterminate in the second port for receiving the fluid. In thisarrangement, the housing may have a pistol-like shape. However, inanother embodiment, the branched passageway may have a more compactconfiguration, in which the different lengths of the passageway runsubstantially parallel to each other. In this arrangement, the housingmay be an elongate capsule sized to fit in an operator's hand.

The interface joint may be particular suitable for gathering a pluralityof inputs into a single cable assembly (i.e. the multi-lumen cableassembly mentioned above) before it is inserted through the instrumentchannel of an endoscope. To achieve this, the cable assembly may have anouter diameter of 9 mm or less, e.g. 2.8 mm or less for a flexible videocolonoscope.

In order to facilitate manipulation of the instrument at the distal endof the instrument channel of the endoscope, the flexible sleeve may beprovided with longitudinal braids therein to assist in the transfer oftorque, i.e. to transfer a twisting motion at the proximal end of thecable assembly to the distal end of the cable assembly, where it cancause bi-rotational rotation of the instrument because the instrument isattached to the cable assembly. The flexible sleeve may comprises ainner tube and an outer tube, which are bonded or otherwise attachedtogether with a tube of metallised braiding in between. The pitch of thebraiding may be variable along the length of the cable assembly. Forexample, it may be useful to have a wider pitch in a region e.g. adistal portion of the cable, where flexibility is important. In order toprevent the metallised braiding from interfering with the RF field ormicrowave field at the instrument, a distal portion of the flexiblesleeve may be provided in which the braided is absent. The distalportion may be manufactured separately and attached (e.g. bonded orwelded) to the braided portion.

The housing may further comprise a strain relief element mounted in theoutlet and surrounding the flexible sleeve. The function of the strainrelief element is to limit the movement of the sleeve in this locationto prevent overflexing that may damage the internal components.

The flexible sleeve may comprise a multi lumen tube. The lumens may beformed by inserting an extruded separator element inside a single lumentube. The extruded separator element may include a plurality of throughchannels (e.g. two, three or more). One of the through channels maycarry the push rod (if present). The other channels may be left empty,which can ensure that there is always a open fluid flow path between theinstrument and interface joint for guiding the coaxial cable and one ormore through holes for carrying the fluid feed conduit and controlwire(s). The fluid flow path may flood the internal cavity formed by theflexible sleeve, and the coaxial cable may be immersed in the fluid.

A distal end of the push rod may be connected to a proximal end of aneedle ferrule, which has a needle clamped to its distal end. Theferrule may be hollow, with one or more openings in its outer wall thatcause its interior to be in fluid communication with the fluid flow paththrough the flexible sleeve. The distal end of the ferrule may be opensuch that the needle mounted in the distal end is in fluid communicationwith the fluid flow path. The proximal end of the ferrule may be sealedby the push rod.

According to the third aspect of the invention, there is provided atorque transfer unit for rotating an electrosurgical instrument at thedistal end of an endoscope by transferring a user's rotating force to aflexible sleeve connected to the electrosurgical instrument, wherein thetorque transfer unit comprises an elongate clamp arranged to impart agripping force along a length of the flexible sleeve that lies outsidethe endoscope, the elongate clamp comprising: an upper elongate housingmember, a lower elongate housing member pivotably connected to the upperelongate housing member and defining a passage for the flexible sleeve,wherein the upper elongate housing member and the lower elongate housingmember are pivotable between a release position in which the torquetransfer unit is slidable up and down the flexible sleeve, and aclamping position, in which the flexible sleeve is gripped between theupper elongate housing member and the lower elongate housing member.

The torque transfer unit may thus be designed to slide freely along thelength of the flexible sleeve to a position that is convenient for use.Once in position, the torque transfer unit can grip the sleeve bypivoting the upper elongate housing member and the lower elongatehousing member together. The torque transfer unit may include areleasable clip that allows the upper elongate housing member and thelower elongate housing member to be locked in place at any point. Theclip may be a resilient latch element on one of the upper elongatehousing member and the lower elongate housing member, which acorresponding catch on the other.

The upper elongate housing member and the lower elongate housing membermay each carry a U-shaped clamping member, the U-shaped clamping membersbeing arranged to oppose one another to impart a substantially uniformgripping pressure on the flexible sleeve when the upper elongate housingmember and the lower elongate housing member are in the clampingposition. In a preferred embodiment, an intermediate deformable griptube is position around the flexible sleeve between the flexible sleeveand the U-shaped clamping members. The intermediate grip tube may bemade of silicone or any other suitable compliant material. In use theintermediate deformable grip tube grips the flexible sleeve oncompression and fixes the position of the torque transfer unit. Theintermediate grip tube acts to distribute the load on the flexiblesleeve which can prevent local damage to the wall of the sleeve.

In use, when the distal tip of the electrosurgical instrument iscorrectly positioned relative to the distal end of the flexibleendoscope within the field of view on the endoscope's video monitor, itis intended that the endoscopist clamps and locks the torque transferunit at the exit point of the flexible shaft from the endoscope workingchannel and immediately adjacent to the endoscope X-Y controls. Whenclamped in this location the torque transfer unit provides finger andthumb rotary and longitudinal positional control of the distal tip ofthe instrument. The variable positioning and clamping of the torquetransfer unit allows the instrument to be used endoscopes of differinglengths (e.g. flexible endoscopes with working channels anywhere between60 and 170 cm long).

Herein, radiofrequency (RF) may mean a stable fixed frequency in therange 10 kHz to 300 MHz and microwave frequency may mean a stable fixedfrequency in the range 300 MHz to 100 GHz. The RF energy should have afrequency high enough to prevent the energy from causing nervestimulation and low enough to prevent the energy from causing tissueblanching or unnecessary thermal margin or damage to the tissuestructure. Preferred spot frequencies for the RF energy include any oneor more of: 100 kHz, 250 kHz, 400 kHz, 500 kHz, 1 MHz, 5 MHz. Preferredspot frequencies for the microwave energy include 915 MHz, 2.45 GHz, 5.8GHz, 14.5 GHz, 24 GHz.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples embodying the invention as discussed in detail below withreference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a complete electrosurgery system in whichthe present invention is applied;

FIG. 2 is a cross-sectional view of an interface joint that is anembodiment of the invention;

FIG. 3 is a cut away perspective view of the interface joint shown inFIG. 2;

FIG. 4A is an exploded view of a torque transfer unit that is anembodiment of the invention;

FIG. 4B is a perspective view of the torque transfer unit of FIG. 4A inan assembled state;

FIG. 5 is a schematic perspective view of another interface joint thatis an embodiment of the invention;

FIG. 6 is a schematic perspective view of an integrated interface jointand torque transfer unit that is an embodiment of the invention;

FIG. 7 is a schematic perspective view of another integrated interfacejoint and torque transfer unit that is an embodiment of the invention;

FIG. 8 is an exploded view of a distal end assembly for anelectrosurgery device that is an embodiment of the invention;

FIG. 9A is a top perspective view of the distal end assembly of FIG. 8in an assembled state;

FIG. 9B is a bottom perspective view of the distal end assembly of FIG.8 in an assembled state;

FIG. 10 is a cross-sectional view of an interface cable suitable for usewith the present invention;

FIG. 11A is a top view of a bipolar structure used in the distal endassembly of FIG. 8;

FIG. 11B is a side view of a bipolar structure used in the distal endassembly of FIG. 8;

FIG. 11C is a bottom view of a bipolar structure used in the distal endassembly of FIG. 8;

FIG. 12A is view of a needle assembly suitable for use with the distalend assembly of FIG. 8;

FIG. 12B is an enlarged cross-sectional view through the needle assemblyshown in FIG. 12A;

FIG. 13 is a schematic drawing illustrating a fluid flow path through aninterface cable that is suitable for use with the present invention;

FIG. 14A is a top view of a protective hull used in the distal endassembly of FIG. 8;

FIG. 14B is a cross-sectional view through the protective hull used inthe distal end assembly of FIG. 8;

FIG. 15A is a perspective view of a stopper used in the interface jointshown in FIG. 2;

FIG. 15B is a cross-sectional view through the stopper shown in FIG.15A;

FIG. 16A is a perspective view of a Y-shaped connector used in theinterface joint shown in FIG. 2;

FIG. 16B is a cross-sectional view through the Y-shaped connector shownin FIG. 16A;

FIG. 17A is an isometric view of various stages in the fabrication of adistal end assembly for an electrosurgery device that is an embodimentof the invention; and

FIG. 17B is an end view of the complete distal end assembly shown inFIG. 17A.

DETAILED DESCRIPTION; FURTHER OPTIONS AND PREFERENCES

Various aspects of the present inventions are presented below in thecontext of an electrosurgery system that provides an electrosurgicalinvasive instrument for use in endoscopic procedures for the removal ofpolyps and malignant growths through the controlled delivery of bothmicrowave and RF energy. However, it is to be understood that theaspects of the invention presented herein need not be limited to thisparticular application. They may be equally applicable in embodimentswhere only RF energy is required, or where only RF energy and fluiddelivery is required.

FIG. 1 is a schematic diagram of a complete electrosurgery system 100that is capable of selectively supplying to the distal end of aninvasive electrosurgical instrument any or all of RF energy, microwaveenergy and fluid, e.g. saline or hyaluronic acid. The system 100comprises a generator 102 for controllable supplying RF electromagnetic(EM) energy and/or microwave frequency EM energy. A suitable generatorfor this purpose is described in WO 2012/076844, which is incorporatedherein by reference.

The generator 102 is connected to an interface joint 106 by an interfacecable 104. The interface joint 106 is also connected to receive a fluidsupply 107 from a fluid delivery device 108, such as a syringe. Theinterface joint 106 houses a needle movement mechanism that is operableby sliding a trigger 110. The function of the interface joint 106 is tocombine the inputs from the generator 102, fluid delivery device 108 andneedle movement mechanism into a single flexible shaft 112, whichextends from the distal end of the interface joint 106. The internalconfiguration of the interface joint 106 is discussed in more detailbelow.

The flexible shaft 112 is insertable through the entire length of aninstrument (working) channel of an endoscope 114. A torque transfer unit116 is mounted on a proximal length of the shaft 112 between theinterface joint 106 and endoscope 114. The torque transfer unit 116engages the shaft to permit it to be rotated within the instrumentchannel of the endoscope 114.

The flexible shaft 112 has a distal assembly 118 that is shaped to passthrough the instrument channel of the endoscope 114 and protrude (e.g.inside the patient) at the distal end of the endoscope's tube. Thedistal end assembly includes an active tip for delivering RF EM energyand/or microwave EM energy into biological tissue and a retractablehypodermic needle for delivering fluid. These combined technologiesprovide a unique solution for cutting and destroying unwanted tissue andthe ability to seal blood vessels around the targeted area. Through useof the retractable hypodermic needle, the surgeon is able to injectsaline and/or hyaluronic acid with added marker dye between tissueslayers in order to distend and mark the position of a lesion to betreated. The injection of fluid in this manner lifts and separates thetissue layers making it both easier to resect around the lesion andplane through the submucosal layer, reducing the risk of bowel wallperforation and unnecessary thermal damage to the muscle layer.

As discussed in more detail below, the distal assembly 118 furtherincludes a protective polymer hull positioned under the active tip toassist a tissue planing type resection action, again helping to protectagainst inadvertent perforation and ensure viability of the remainingtissue, which in turn facilitates more rapid healing and post operationrecovery.

The structure of the distal assembly discussed below may be particularlydesigned for use with a conventional steerable flexible endoscope havinga working channel with an internal diameters of at least 2.8 mm and achannel length of between 60 cm and 170 cm. As such the majority of thecomparatively small diameter (less than 3 mm) instrument is housedwithin the lumen of a much larger and predominantly polymer insulatingdevice, i.e. the flexible endoscope channel, which typically has anouter diameter of 11 mm to 13 mm. In practice, only 15 mm to 25 mm ofthe distal assembly protrudes from the distal end of the endoscopechannel, in order not to block the field of view or adversely affectcamera focussing. The protruding part of the distal assembly is the onlyportion of the instrument that ever makes direct contact with thepatient.

At the proximal end of the endoscope working channel, which is typicallyheld 50 cm to 80 cm from the patient, the flexible shaft 112 emergesfrom the working channel port and extends a further 30 cm to 100 cm tothe interface joint 106. In use, the interface joint 106 is typicallyheld by a gloved assistant throughout the procedure. The interface joint106 is designed and manufactured from polymer materials in such a way asto provide primary and secondary electrical insulation with extendedcreepage and clearance distances. The interface cable 104 is connectedto the generator 102 using a QMA-type coaxial interface, which isdesigned to allow continuous clockwise or counter clockwise rotation.This permits the interface joint 106 to rotate with the torque transferunit 116 under the control of the endoscopist. The assistant supportsthe interface joint 106 throughout the procedure in order to assist theendoscopist with sympathetic instrument rotation, needle control andfluid injection.

Interface Joint & Torque Transfer Unit

FIGS. 2 and 3 show the structure of an interface joint 120 that is anembodiment of the invention. The interface joint comprises a hardplastic shell 122, which encases several internal components. In FIGS. 2and 3 one half of the shell 122 is removed to show the inside of thejoint. The shell 122 is in the shape of a pistol, i.e. it has an upperbarrel portion 121 and a lower adjoining portion 123 which extends awayfrom a proximal end of the upper barrel portion at an oblique angle. Theupper barrel portion 121 contains the needle movement mechanism, whilethe lower adjoining portion 123 contains the connections for the fluidand energy feeds.

The core of the interface joint 120 is a pair of Y-shaped conduits 124,126 which are mated together to define a branched passageway. TheY-shaped conduits may be made from polycarbonate or other suitable hardplastic, and are shown in more detail in FIGS. 16A and 16B. A firstlength 128 of the branched passageway is mounted in and lies along theupper barrel portion 121 of the shell 122. The first length 128 receivesat its proximal end a push rod 130 for controlling deployment of theretractable needle. The push rod 130 has a crooked proximal end 132,which is mounted, e.g. heat staked, in a needle slider 134. The needleslider 134 is slidably mounted in the upper barrel portion 131. Theneedle slider 134 includes a protruding thumb trigger 136 for moving theslider to and fro, which causes the needle to slide in and out of thedistal assembly. The proximal end of the first length 128 is sealed by asilicone bung 138, which is shown in more detail in FIGS. 15A and 15B.

A second length 140 of the branched passageway is mounted in and liesalong the lower adjoining portion 123, i.e. at an oblique angle to thefirst length 128. The second length 140 conveys a coaxial cable 142 froma proximal QMA-type connector 144 to the proximal end of the firstlength 128, where it meets the push rod 130 and exits the interfacejoint 120 through the distal outlet 146. The QMA-type connector 144 isconnected to the interface cable from the generator. The coaxial cable142 may be a Sucoform 047 coaxial cable coated in a 30.mu.m layer ofParylene C. The coaxial cable 142 may pass through a silicone sealingplug 148 at the proximal end of the second length 140.

A third length 150 of the branched passageway leads off from the secondlength 140 to provide a outward facing fluid receiving port 152. Thefluid receiving port 152 may be a threaded luer lock fitting, forsealing engagement with a suitable syringe or the like. The sealing plug148 and the bung 138 cause the branched passageway to be sealed in awatertight manner, whereby fluid introduced at the fluid receiving port152 can only exit the interface joint 120 through the distal outlet 146.

The distal outlet 146 of the interface joint receives therethrough aproximal portion of the flexible shaft 154 that is introduced into theinstrument channel of the endoscope. The flexible shaft conveys thefluid, push rod 130 and coaxial cable 142 as discussed below. A proximalend of the flexible shaft 154 is directly bonded into the branchedpassageway so that there is some overlap along the upper barrel portion121. This bonded junction is masked by a covering 156 (e.g. of siliconerubber) which fits like a stretched glove and is bonded in place. Thecovering 156 operates as a strain relief element, and also doubles as anend of shaft flexible bend restrictor.

The primary user of the interface joint 120 may be the endoscopist'sassistant. In use, the operator typically offers the distal tip of theinstrument to the endoscopist for insertion down the working channel ofthe flexible endoscope, makes the electrical connection betweeninterface joint 120 and the interface cable (which is connected to thegenerator) and then supports the interface joint 120 itself throughoutthe procedure. During the procedure the operator can inject thedistension/marker fluids as required via 5 to 20 ml syringes attached tothe fluid receiving port 152 and operate the needle slider 134 asinstructed by the endoscopist.

The flexible shaft 154 comprises an outer cannula tube that contains thecoaxial cable 142, push rod 130 and fluid. The specific internalstructure of the flexible shaft is discussed below with reference toFIG. 10. The distal assembly is fixed to the outer cannula tube in amanner that means any rotation applied to the tube is passed to thedistal assembly. Accordingly, to permit rotatable manipulation of thedistal assembly, a torque transfer unit is mounted on the flexible shaftin order to facilitate rotation thereof.

FIGS. 4A and 4B show a torque transfer unit 158 that is an embodiment ofthe invention. Essentially the torque transfer unit 158 is an elongateclamp that imparts a gripping force along a length of the flexibleshaft. By gripping a length of the shaft, the torque transfer unit canapply a lower maximum pressure, and therefore prevent damage to theflexible shaft and its contents.

As shown in FIG. 4A, the torque transfer unit 158 comprises an upperelongate housing member 160 and a lower elongate housing member 162,which are hinged together about a pivot rod 164 at a distal end thereof.The upper elongate housing member 160 and the lower elongate housingmember 162 each carry a U-shaped clamping member therein 166. Theclamping members 166 oppose one another, whereby pivoting the upperelongate housing member 160 and the lower elongate housing member 162relative to each other alters the distance between the clamping members166. A deformable tube 168 is mounted between the clamping members 166.The deformable tube 168 is threaded on to the flexible shaft, whichpasses though holes 170 in the distal and proximal faces of the torquetransfer unit 158. In use, the upper elongate housing member 160 and thelower elongate housing member 162 are pivotable between a releaseposition in which the torque transfer unit can be slid up and down theflexible shaft, and a clamping position, in which the deformable tube168 is squashed between the clamping members to impart a gripping forceon the flexible shaft. The upper elongate housing member 160 and thelower elongate housing member 162 can be retained in the clampingposition by a releasable clip 172. The distal end of the torque transferunit 158 has a series of circumferential indentations designed to begripped by the thumb and forefinger of the operator, to facilitaterotation.

FIG. 5 is a perspective view of an interface joint 180 in conjunctionwith a torque transfer unit 158 that is another embodiment of theinvention. The torque transfer unit 158 is the same as that discussedabove with reference to FIGS. 4A and 4B and is not discussed again.

The interface joint 180 in this embodiment comprises a compactbarrel-like body 182, which facilitates rotation by the endoscopist'sassistant. In particular, the interface cable 104 is connected in axialalignment with the body 182, e.g. via a snap-fit rotary coaxialconnector. The body 182 includes a nested barrel 184 for receiving asyringe 188 to deliver fluid. The nested barrel 184 may include aviewing window 186 to show how much fluid remains.

In this embodiment, a needle slider control 190 is mounted towards thenose of the body 180 for thumb control whilst the body 182 is supportedin the palm of the hand. The slider 190 may have free reciprocalmovement as in the embodiment shown in FIGS. 2 and 3. A latch mechanism(not shown) may be provided to lock and park the slider in the fullyretracted needle position. Alternatively the slider may have aspring-loaded action which biases the mechanism into the retractedstate. With the sprung loaded option the user (assistant) would need tohold the slider forward against the spring whilst injecting the fluid.

FIG. 6 is a perspective view of a combined interface joint and torquetransfer unit 192 that is another embodiment of the invention. Allfunctions of the separate torque transfer unit and interface jointsdiscussed above are provided here within a single moulded assembly.However, the combined unit is not able to slide along the flexible shaftin use, which means that the instrument length should be closely matchedto the endoscope working channel length. However, an advantage of thisarrangement is that there is more microwave power available at theactive tip in the distal assembly because a shorter instrument lengthmeans less power is lost.

The combined unit 192 comprises a waisted barrel 194 with a faceteddistal end 196 to facilitate easy finger and thumb rotary control. Aneedle slider 198 is mounted towards the back of the barrel 194 due tothe natural hold and support position by the endoscopist during theseprocedures.

As an alternative to the needle slider 198, a hinged rocker type controllever could be used for ease of thumb control. With this design needleslider (or rocker) latch forward and back would be required or latchback and sprung forward control to enable one handed operation and fluidinjection by the endoscopist, i.e. to give the endoscopist the freedomto use their second hand to hold or manipulate the endoscope.

FIG. 7 is a perspective view of a combined interface joint and torquetransfer unit 200 that is another embodiment of the invention. Thecombined unit 200 is similar to the device shown in FIG. 6 except for aremote syringe fluid injection coupling 201. The combined unit 200comprises a slim barrel-like body 202 with a faceted distal end 204 anda needle slider 206 which function as discussed above. The body 202 hasa slim, compact design because it does not also need to house a syringe.Instead, the body 202 is connected to a fluid receiving port 208 via afluid feed line 210. This arrangement may permit the device to be usedwith larger syringes of unrestricted barrel diameter. The body in thisarrangement may also be more lightweight than that shown in FIG. 6. Inthis embodiment the distal end 204 of the body 202 includes a recessedflat face 212, which allows abutted location against the endoscope portcap for added stability. As with this device shown in FIG. 6, thissolution (as shown) requires the instrument length to be closely matchedto the third party endoscope working channel length, and thereby offersthe potential for more microwave power availability at the instrumenttip.

It may be possible to build in short axial adjustment of up to 100 mmwithin the combined barrel-shaped units shown in FIGS. 6 and 7. This mayenable the endoscopist to fine tune the instrument length to his/herflexible endoscope of choice. This added functionality could alsominimise the number of product variants required to cover the range ofpresent day third party endoscopes.

FIGS. 15A, 15B, 16A and 16B show further details of some of the internalcomponents of the interface joint.

FIGS. 15A and 15B are respectively perspective and cross-sectional viewsof the bung 138 that seals the proximal end of the first length of thebranched passageway. The bung comprises a rotary luer lock fitting 246and a integral sealing diaphragm 248, e.g. made of resilientlydeformable rubber.

FIGS. 16A and 16B show the Y-shaped conduits 250 from which the branchedpassageway is formed. Each Y-shaped conduit has a main linear channelbetween a first inlet 252 and an outlet 254, and a second channel at anoblique angle to the main linear channel, the second channel having asecond inlet 256 and joining the main linear channel about halfway alongits length. Each of the first inlet 252 and the second inlet 256 has arotary luer lock fitting 258.

Distal Assembly Configuration

FIGS. 8, 9A and 9B show details of a distal assembly 214 comprising anactive tip that is an embodiment of the invention. FIG. 8 shows anexploded view of the components that form the distal assembly 214. Thedistal assembly 214 is mounted at the distal end of the outer cannulatube 216 of the flexible shaft 154 that is discussed above. In order toprovide a torque transfer function, the majority of the outer cannulatube 216 is formed of a braided tube, e.g. comprising a braided wire(e.g. stainless steel) wrap mounted between a radially inner polymerlayer and a radially outer polymer layer. However, to avoid the braidmaterial from interfering with the deliver of RF and/or microwavefrequency EM energy to the distal assembly, a distal portion 218 of theouter cannula tube 216 is made purely of the polymer layers, i.e.without an internal braid.

The distal portion 218 of the outer cannula layer 216 fits on to acorresponding proximal part 220 of a protective hull 222. The protectivehull is formed from polyether ether ketone (PEEK) or any other suitableengineering plastic, and is shaped to perform a number of functions,i.e.

-   -   mount the distal assembly on the flexible shaft,    -   provide a protective undersurface for the active tip,    -   provide a protective housing for the needle, and    -   locate the active tip relative to the coaxial cable.        The parts of the structure of the hull 222 that perform these        functions are discussed in more detail below with reference to        FIGS. 14A and 14B.

The distal assembly 214 includes an active tip 224, which is a planarpiece of dielectric material (e.g. alumina) having conductive layers(e.g. of gold) on its upper and lower surfaces. The distal end of theactive tip 224 is curved. The conductive layers are electricallyconnected to the inner and outer conductors of the coaxial cable 142that is conveyed by the flexible shaft 216. At the distal end of thecoaxial cable 142, its outer sheath is removed to expose a length of theouter conductor 226. The inner conductor 228 of the coaxial cableextends beyond the distal end of the outer conductor 226. The coaxialcable 142 and the active tip 224 are mounted relative to one another sothat the protruding part of the inner conductor 228 lies on a firstconductive layer of the active tip, while the outer conductor 226 isbrought into electrical connection with a second conductive layer by aconductive adaptor element 230. The first conductive layer is isolatedfrom the outer conductor 226 and the second conductive layer is isolatedfrom the inner conductor 228. Further details of the configuration ofthe active tip are discussed below with reference to FIGS. 11A to 11C.

When assembled, as shown in FIGS. 9A and 9B, the active tip 224 andcoaxial cable 142 are bonded to each other and to the hull 222 by theapplication of epoxy adhesive over the portion of the inner conductor228 that projects from the outer conductor. This epoxy adhesive alsoserves to form an end plug for the outer cannula tube, i.e. a fluidtight seal that means the only exit for fluid introduced at theinterface joint is through the needle.

The hull 222 includes a recess for retaining a needle guide tube 232,e.g. made of polyimide. In use the distal assembly 214 makes an intimatecontact with the patient. The needle 234 can be extended beyond thedistal end of the active tip 224 and retracted to a position back insidethe guide tube 232 via control of the slider mechanism on the interfacejoint. In its extended position, the needle is used by the endoscopistto inject fluid for the purpose of locally distending and markingtissue. The conductive layers on the active tip 224 form bi-polarelectrodes for delivering RF and/or microwave frequency energy.

The needle guide 232 extends back inside and proximal to the distalassembly to provide extended creepage clearance to ensure RF/microwaveactivation only occurs across the distal tip region of the active tip224.

Similarly it can be seen that the conductive layer 236 is recessed backin behind the distal tip region of the active tip 224. This is done onboth upper and lower faces to increase the tracking/creepage distance atthe proximal end of the active tip, further ensuring that RF/microwaveenergy is focused towards the distal end and intentional active elementof the tip.

FIG. 10 shows a typical cross section of the flexible shaft 154. Theflexible shaft may run for 2.3 m (or 2.0 m), i.e. the entire length ofthe instrument connecting the interface joint to the distal assembly.During use the majority of this shaft length sits within the workingchannel of the flexible endoscope. The flexible shaft 154 comprises theouter cannula tube 216 (i.e. the braided tube discussed above), whichforms a fluid tight cannula 237 and electrical barrier betweenuser/patient, and the coaxial Sucoform cable 142 which in itself isfurther insulated. The outer cannula tube 216 also houses a 3-lumen PTFEextruded tube 238 which provides a low friction pathway for the push rod130 and stability/support to the construction whilst ensuring a fluidpathway is maintained along the full length of the cannula at all times.

Through the length of the flexible shaft 154, the coaxial cable 142(e.g. Sucoform 047 cable) forms one lumen of a composite constructionwith the braided and double insulated outer cannula tube 216 forming theflexible protective instrument shaft. To manage the potential thermalrisk posed in use activation controls may be imposed on the use ofmicrowave energy by the generator. For example, in the first applicationinstance activation may be limited to 20 s (continuous output), andthereafter the average power incidence on the proximal end of the distalassembly may be limited to 4 W. This control may be imposedindependently of the endoscopist, e.g. via the generator software. Withthis control in place a temperature of 40° C. has been observed after 20s continuous activation on the polymer surface of the instrument shaftimmediately distal of the interface joint. After 20 s the temperaturethen falls as further continuous microwave activation by the Endoscopistis automatically interrupted by the generator software. Full 20 sactivation capacity may be prevented until 240 s (12×20 s) has elapsed.

In practice, it may not be necessary to activate the coagulationfunction for longer than 10 s due to concerns over perfusion at the tipresulting in potential full wall thickness injury to the bowel wall.

FIGS. 11A, 11B and 11C illustrate the dimensions of one example of anactive tip 224 that can be used in embodiments of the invention. Theoverall length of the active tip is 10.6 mm, with a maximum width of 2mm and a height of 0.5 mm. The layer of metallisation on the active tiphas a thickness of 0.03 mm. The curved distal end is manufactured as aplurality of radiused sections of decreasing length and radius towardsthe distal tip. In this embodiment there are five different radiusedsection, but more could be used. The length of each section and itscorresponding radius of curvature is given in Table 1:

TABLE 1 Curvature at distal end of active tip Section length (mm) Radiusof Curvature (mm) 1.6 12.4 1.0 10.2 0.7 3.2 0.2 0.85 0.1 0.35

As mentioned above, the conductive layers on both surface are set backfrom the edges of the dielectric substrate by a distance of 0.2 mm alongthe proximal 6 mm of the tip. And to ensure that the top conductivelayer is isolated from the outer conductor of the coaxial cable, the topconductive layer is set back from the proximal edge of the dielectricsubstrate by a distance of 0.6 mm.

FIGS. 12A and 12B depict the transition from the push rod 130 to theneedle 234. A needle ferrule 240 is connected to the push rod 130 at aproximal end thereof and is connected to the needle 234 at a distal endthereof. A set of holes in the outer surface of the needle ferrule 240permits ingress of fluid from the flexible shaft for delivery out of theneedle 234. As shown in FIG. 12B, the push rod 130 acts as a stopper inthe proximal end of the ferrule 240, thereby preventing fluid fromescaping in the wrong direction.

FIG. 13 illustrates schematically the flow path for the fluid.Immediately proximal of the distal assembly the injected fluid that haspassed down the flexible shaft 154 from the syringe is forced throughfour small radial holes 242 central to the needle ferrule 240 and thenceinto the hypodermic needle 234 for injection into the patient.

FIGS. 14A and 14B show the shape of the protective hull 222. As shownmore clearly in FIG. 9B, the distal end of the hull is shaped to permitthe active tip to overhang it by around 0.2 mm around the distal edgeexcept at the distal tip. The surface that contacts the underside of theactive tip therefore has a maximum width of 2 mm, which narrows to 1.6mm in an intermediate portion 223 before tapering to its distal tip in adistal portion 225. The distal tip may be a single radiused curve, e.g.having a radius of 0.2 mm.

Meanwhile the proximal end of the hull defines an oblong recess forreceiving the proximal end of the active tip. The oblong recess isbordered by a pair of wings 244 on each side, which act to retain andalign the active tip as well as define a volume for receiving theadhesive that covers the exposed inner conductor of the coaxial cable.

FIG. 17A shows various stages in the assembly of a distal end portion300 for an electrosurgical instrument that is another embodiment of theinvention. The leftmost view in FIG. 17A shows an inner tube 302 made ofa conductive material. This inner tube 302 represents the innerconductor of the coaxial feed discussed above. The second view from leftin FIG. 17A shows an outer tube 304, which first over the inner tube302. The outer tube 304 may be formed as a tube of insulating dielectricmaterial having a conductive coating on its outer surface. Theconductive coating acts as the outer conductor of the coaxial feed.

At the distal end of the outer tube, a portion of the conductive coatingis etched away to expose a portion 306 of dielectric material. An island308 of conductive coating is left on the top surface of the outer tubeat its distal end. The island 308 is separated (i.e. electricallyisolated) from the rest of the conductive coating 304 by the exposedportion 306 of dielectric material. A tongue (not shown) of conductivecoating is formed on the bottom surface of the outer tube at its distalend with a similar shape and size to the island 308. However, the tongueremains in electrical contact with the rest of the conductive coating,i.e. it is an extension of the outer conductor.

A hole 310 (e.g. having a diameter of 1 mm) is formed in the island 308through the conductive coating and insulating dielectric material,thereby exposing the inner tube 302. The hole is then filled with aconductive material (e.g. epoxy silver) in order to electrically connectthe inner tube 302 with the island 308. As a result, the distal end ofthe outer tube has two opposed electrical contacts on its outer surface.A first contact (the island 308) is in electrical connection with theinner tube 302 (i.e. inner conductor) and a second contact (the tongue)is in electrical connection with the conductive coating of the outertube 304 (i.e. outer conductor).

The third view from left in FIG. 17A shows the next stage in assembly,where an instrument tip 312 is inserted into the distal end of the outertube 304. The instrument tip 312 comprises a planar piece 314 of rigiddielectric, e.g. ceramic, such as alumina. The outer tube 304 has twoopposing tabs 316, which can receive and retain the planar piece 314,e.g. as an interference fit or using suitable adhesive.

The side edges of the planar piece 314 taper in a quasi-parabolic mannertowards the distal end thereof. The flat upper and lower surfaces haveconductive layers, e.g. of gold or silver metallisation, formed thereon.The upper layer 318 is visible in FIG. 17A.

The right most view in FIG. 17A shows the final stage of assembly, inwhich the first and second contacts are electrically connectedrespectively to the upper and lower conductive layers on the instrumenttip 312 using a piece of conductive foil 318.

FIG. 17B shows an end view of the distal end portion 300 after assembly.Here it can be seen that the lower piece of conductive foil 320 has ahole 322 formed therein through which the retractable needle discussedabove can pass.

1. An interface joint for interconnecting an electrosurgical generatorand an electrosurgical instrument, the interface joint comprising: ahousing made of electrically insulating material, the housing having: afirst inlet for receiving radiofrequency (RF) electromagnetic (EM)energy or microwave frequency EM energy from the electrosurgicalgenerator, a second inlet for receiving fluid, and an outlet; a singlecable assembly for connecting the outlet to the electrosurgicalinstrument, the signal cable assembly comprising a flexible sleeve thatdefines a fluid flow path that is in fluid communication with the secondinlet, and which conveys a coaxial cable that is connected to the firstinlet.
 2. An interface joint according to claim 1, wherein the housingincludes an internal watertight branched passageway which defines afluid flow path between the second inlet and the outlet, and wherein thebranched passageway has a first port adjacent to the first inlet foradmitting the coaxial cable.
 3. An interface joint according to claim 1including a slidable trigger on the housing, the slidable trigger beingattached to a push rod that extends out of the housing through theoutlet.
 4. An interface joint according to claim 3, wherein the housingincludes an internal watertight branched passageway which defines afluid flow path between the second inlet and the outlet, and wherein thebranched passageway has a first port adjacent to the first inlet foradmitting the coaxial cable and a second port adjacent the slidabletrigger for admitting the push rod.
 5. An interface joint according toclaim 2, wherein the first port comprising a sealing bung which definesa watertight passage for the coaxial cable.
 6. An interface jointaccording to claim 2, wherein the second port comprises a sealing bungwhich defines a watertight passage for the push rod.
 7. An interfacejoint according to claim 2, wherein the internal watertight branchedpassageway is formed from a pair of Y-shaped conduits.
 8. An interfacejoint according to claim 1, wherein the cable assembly has an outerdiameter in the range 1.2 mm to 9 mm.
 9. An interface joint according toclaim 1, wherein the flexible sleeve has spiral wound reinforcement orspiral wound multiple cross braiding therein to assist in the transferof torque.
 10. An interface joint according to claim 9, wherein thespiral wound reinforcement or spiral wound multiple cross braiding has avariable pitch.
 11. An interface joint according to claim 1, wherein thehousing comprises a strain relief element mounted in the outlet andsurrounding the flexible sleeve.
 12. An interface joint according toclaim 1 having a coaxial cable attached to the first inlet via interfaceconnection, wherein the interface connection is arranged to permitrelative rotation of the interface joint relative to the coaxial cable.13. An interface joint according to claim 1, wherein the flexible sleevecomprises a multi lumen tube.
 14. An interface joint according to claim13, wherein the flexible sleeve includes an extruded separator elementinserted inside a single lumen tube, the extruded separator elementincluding a plurality of through channels.
 15. An interface jointaccording to claim 4, wherein a distal end of the push rod is connectedto a proximal end of a needle ferrule, which has an internal volume influid communication with the fluid flow path through the flexiblesleeve, and wherein a needle is mounted in the distal end of the needleferrule in fluid communication with the internal volume.
 16. Aninterface joint according to claim 1, wherein the housing is an elongatecapsule sized to fit in an operator's hand.